The present disclosure relates to a nonaqueous electrolyte secondary battery and a separator.
In recent years, a number of portable electronic appliances such as a camera-integrated VTR, a digital still camera, a mobile phone, a personal digital assistant and a laptop computer have appeared, and it is contrived to achieve downsizing and weight reduction thereof. With respect to batteries, in particular, secondary batteries as a portable power source for such an electronic appliance, research and development have been actively conducted for the purpose of enhancing the energy density.
Above all, lithium ion secondary batteries utilizing intercalation and deintercalation of lithium for a charge and discharge reaction are widely put into practical use because a large energy density is obtained as compared with lead batteries and nickel-cadmium batteries which are a nonaqueous electrolytic solution secondary battery of the related art.
In these lithium ion secondary batteries, for the purpose of enhancing the battery capacity, it is proposed to use a negative electrode material including silicon or tin as a composing element as a negative electrode active material (see, for example, JP-A-2007-188777).
Also, in the lithium ion secondary batteries, a polyolefin separator having a shutdown function is widely used as an insulating material for preventing a short circuit between electrodes from occurring.